Multichannel communications in unlicensed spectrum

Abstract

A method and apparatus for communicating on multiple channels in a data replication communication, possibly in an unlicensed spectrum. The method includes scanning multiple channels in the unlicensed spectrum to determine whether the multiple channels are available. In response to determining that at least one of the channels is available, determining when a transmission opportunity may occur and estimating at least one delay between the transmission opportunity and at least one additional transmission opportunity, wherein the apparatus is estimated to be able to transmit a signal on the at least one additional channel in the multiple channels at the at least one additional transmission opportunity. Determining whether any of the at least one delay is within a current delay tolerance and, if not, transmitting the signal on the available channel; and, if so, delaying transmitting the signal until another transmission opportunity is within the current delay tolerance.

Description

Technical Field

[0001] Various example embodiments relate to communications within an unlicensed spectrum. Background Art

[0002] Unlicensed spectrum offers the opportunity to increase the bandwidth available for transmitted signals. However, because this bandwidth is shared with other devices, some scanning of the channel may be required before transmission to reduce interference. Additionally, there may be regulations regarding how often devices can scan the channel to ensure fair sharing of the spectrum, and these issues can lead to increased latency.

[0003] Unlicensed bands are divided into sub-bands or channels, each covering a specific frequency band, and scanning processes such as listen-before-talk involve sensing these channels to determine if they are available before transmitting a signal. If a channel is available, the device can acquire the channel within the channel occupation time (COT). During this time, signals can be transmitted, but other devices are blocked from using the channel.

[0004] Devices are increasingly capable of transmitting and receiving on multiple channels. This capability can be combined with data replication across different sub-channels to improve transmission reliability. When transmitting on multiple channels, the transmitter needs to scan each channel separately before transmitting. In cases where channels are close together in a frequency band, it is not possible to scan channels while a transmission is occurring. Therefore, in some cases, it may be desirable to wait for multiple channels to become available before transmitting. However, this can significantly increase latency if one of the channels is blocked.

[0005] It would be desirable to provide a system for communicating in an unlicensed spectrum in an efficient manner while maintaining some control over latency. Summary of the Invention

[0006] The scope of protection sought by various embodiments of the present invention is defined by the independent claims. Embodiments, examples, and features described in this specification that do not fall within the scope of the independent claims (if any) are to be construed as examples useful for understanding various embodiments of the present invention.

[0007] According to various but not necessarily all embodiments of the present invention, there is provided, according to a first aspect, an apparatus comprising a component configured to:

[0008] initiating a scan of a plurality of channels in an unlicensed spectrum to determine whether the plurality of channels are available;

[0009] determining a transmission opportunity in which the apparatus is able to transmit a signal on at least one channel sensed as available during the scanning period;

[0010] When it is estimated that the apparatus may be able to transmit signals on at least one additional channel in the unlicensed spectrum, estimating at least one additional transmission opportunity; and

[0011] confirming whether a delay between the transmission opportunity and the at least one further transmission opportunity is within a current holdover tolerance of the apparatus; and if not

[0012] controlling signal transmission on said at least one available channel; and in the case of yes,

[0013] Waiting for one of the at least one additional transmission opportunities that is within the current holdover tolerance before controlling transmission of at least one signal on the at least one available channel

[0014] Embodiments address contention issues that arise when seeking to transmit signals on different channels of unlicensed spectrum, each of which can potentially increase latency. When a first signal is transmitted at a first transmission opportunity when a channel is sensed as available, scanning to determine the availability of other channels during the transmission period is prevented. If the device waits for one or more additional channels to become available before transmitting the first signal, the device risks excessive delay before transmitting any signals if the additional channels do not become available. These issues are addressed by a device configured so that the decision to transmit or wait is an informed one that considers various factors. Therefore, the device has a deferral margin, which is a period of delay in transmitting a signal that may be set to a level deemed acceptable for a certain desired delay. This can be set as a time period or a counter value, for example, indicating the number of transmission opportunities. The device is configured to assess whether additional channels are likely to become available, or whether it is likely to do so at a future transmission opportunity within the deferral margin. If the device assesses this to be the case, it defers transmission until a subsequent transmission opportunity, then performs the same assessment at that transmission opportunity. If it estimates that no channels will be available within the deferral tolerance, it transmits on the available channel(s). In this way, whether to defer transmission is based on an assessment of whether there is a chance that there will be an opportunity to transmit on another channel within the deferral period, and once it is determined that this is not the case, transmission occurs on the available channel(s) at the next transmission opportunity. In this way, the likelihood that more than one channel can be used to transmit signals increases compared to a device that does not defer, while the increased delay caused by waiting for another channel is managed within certain limits and is only used when such waiting is likely to make additional channels available.

[0015] It should be noted that where the term channel is used, this refers to a frequency band in the unlicensed spectrum that is used to transmit signals to other devices, and the scanning process determines the availability of this frequency band. In the description of the embodiments, this may sometimes be referred to as a sub-channel, link, or sub-band.

[0016] In some embodiments, the component is configured to estimate the time of the at least one additional transmission opportunity for the at least one channel based on at least one of the following: a determined state of the channel and a backoff time associated with the channel, the backoff time being a minimum time delay before a transmission opportunity occurs if the channel is currently idle and remains idle.

[0017] The device can determine whether a transmission opportunity is likely to exist within the postponement tolerance based on a number of factors, and in some cases, it can determine this based on a determined channel state, such as whether the channel is available or idle, and / or based on a backoff time associated with the channel. The backoff time is the minimum time delay before a transmission opportunity occurs if the channel is currently idle and remains idle. Each of these factors affects whether the channel will be available for a subsequent transmission opportunity and can be used by the device to determine whether waiting for such a channel would improve performance.

[0018] In some embodiments, the determined state of the channel comprises one of: a sensed state sensed during a previous measurement time period, or an estimated state based on the sensed state and a historical availability of the channel.

[0019] When making the estimation, the state of the channel is important, and its current state may not be known, but it can be determined based on the state sensed in a previous measurement time period or based on the historical availability of the channel (from which its possible state can be estimated), or based on a combination of previous measurements and historical availability.

[0020] In some embodiments, the previous measurement time period comprises a measurement period immediately preceding a most recent transmission opportunity.

[0021] The more recent the sensed state is, the more likely it is to be accurate, so if the sensed state is a state that was sensed in the immediately most recent measurement time, this may provide a more accurate estimate.

[0022] In some embodiments, the component is configured to determine whether any of the at least one additional channel of the plurality of channels is available at one of the at least one additional transmission opportunities, and if available, the component is configured to control the at least one signal to be transmitted on the at least one available channel and at least one additional signal to be transmitted on the at least one additional available channel at the one additional transmission opportunity of the at least one additional transmission opportunity.

[0023] If the device does postpone transmission and scans for additional channels, where a channel is detected as available, then at the next transmission opportunity the signal may be transmitted on the first channel sensed as available and on any additional channels sensed as available. In this way, multiple channels are used to transmit one or more signals and the reliability and / or bandwidth of the transmission is increased.

[0024] In some embodiments, the component is configured to determine whether all of the at least one further channel of the plurality of channels are busy, and if so, control transmission of the at least one signal on the at least one available channel at a next transmission opportunity.

[0025] In the event that a scan of other channels determines that they are all busy, then there may be no channels available within the postponement tolerance, and the device can then make a decision to transmit on an available channel. In this way, unnecessary delays in transmitting signals while waiting for unavailable channels do not occur.

[0026] In some embodiments, the at least one signal and the at least one further signal are the same signal, the apparatus being configured to transmit a replica signal over a plurality of channels.

[0027] Embodiments may be particularly effective for transmitting duplicate signals on different channels, thereby improving transmission reliability. Where duplicate signals are to be transmitted, allowing them to be transmitted simultaneously on multiple channels is a very effective method for improving reliability. If a signal is transmitted on one channel, there is a delay before subsequent channels can be scanned, and this delay can increase or reliability can decrease if the signal is not a duplicate. Embodiments increase the probability that a signal can be transmitted simultaneously on multiple channels while managing the increased delay that can be introduced by congested channels.

[0028] In some embodiments, the apparatus comprises a user equipment, while in other embodiments, the apparatus comprises a gNB.

[0029] User devices that transmit signals to each other can use this technology to do so. Similarly, gNBs, which correspond to base stations in 5G, can use this technology to transmit signals to one or more devices such as user devices.

[0030] In some embodiments, the one or more signals comprise uplink signals.For example, this may be the case where the apparatus is user equipment.

[0031] In some embodiments, the delay tolerance can be centrally set by the network, and the apparatus can be configured to receive an indication of the delay tolerance from a network node and set the delay tolerance accordingly. The network node can transmit a signal indicating the delay tolerance to be used. In some embodiments, the network node can also transmit additional signals indicating that data replication is to be used and that a specific listen-before-talk scanning process is to be used.

[0032] In other embodiments, the one or more signals include a downlink signal, which may be the case where the apparatus is a gNB.

[0033] In some embodiments, the apparatus comprises:

[0034] at least one processor; and

[0035] At least one memory including computer program code, the at least one memory and computer program code being configured to, with the at least one processor, cause execution of the apparatus.

[0036] In some embodiments, the apparatus further comprises means for transmitting and receiving signals, and means for scanning channels in an unlicensed spectrum.

[0037] According to various but not necessarily all embodiments of the present invention, there is provided a method according to a second aspect, comprising:

[0038] scanning a plurality of channels in an unlicensed spectrum to determine whether the plurality of channels are available;

[0039] In response to determining that at least one of the plurality of channels is available, determining a transmission opportunity in which the apparatus is able to transmit at least one signal on the at least one available channel;

[0040] estimating at least one delay between the transmission opportunity and at least one further transmission opportunity at which it is estimated that the apparatus may be able to transmit a signal on at least one further channel of the plurality of channels; and

[0041] Determine whether any of the at least one delay is within the current postponement tolerance, and if not

[0042] transmitting the at least one signal on the at least one available channel; and

[0043] In the case of

[0044] Transmission of the at least one signal on the at least one available channel is delayed until another transmission opportunity is within the current holdover tolerance.

[0045] In some embodiments, the step of estimating the at least one delay comprises estimating a time of the at least one additional transmission opportunity for the at least one channel based on at least one of: a determined state of the channel and a backoff time associated with the channel, the backoff time being a minimum time delay before a transmission opportunity can occur if the channel is currently idle and remains idle. The determined state of the channel.

[0046] In some embodiments, the determined state of the channel comprises one of: a sensed state sensed during a previous measurement time period, or an estimated state based on the sensed state and a historical availability of the channel.

[0047] In some embodiments, the method further comprises determining whether any of the at least one further channel of the plurality of channels is available at one of the at least one further transmission opportunities, and if available,

[0048] The transmission means is controlled to transmit the at least one signal on the at least one available channel at the further transmission opportunity and to transmit the at least one further signal on the at least one further available channel.

[0049] In some embodiments, the method comprises determining whether all of the at least one further channel of the plurality of channels are busy, and if so controlling the transmission component to transmit the at least one signal on the at least one available channel at a next transmission opportunity.

[0050] In some embodiments, the at least one signal and the at least one further signal are the same signal, and the method transmits a replica signal on a plurality of channels if the plurality of channels are available.

[0051] According to various, but not necessarily all, embodiments of the invention, there is provided according to a third aspect a computer program comprising computer readable instructions which, when executed by a processor on an apparatus, are operable to control the apparatus to perform a method according to the second aspect.

[0052] According to various but not necessarily all embodiments of the present invention, a device is provided, comprising: a scanning circuit configured to scan multiple channels in an unlicensed spectrum to determine whether the channels are available; a transmitter for transmitting one or more signals on one or more of the multiple channels; and a control circuit for controlling the transmission of the one or more signals, the control circuit being configured to start the scanning circuit to scan multiple of the multiple channels to determine whether multiple of the channels are available; determining a transmission opportunity in which the device is able to transmit a signal on at least one channel sensed as available by the scanning circuit; estimating at least one additional transmission opportunity when it is estimated that the device may be able to transmit a signal on at least one additional channel of the multiple channels; and confirming whether the delay between the transmission opportunity and the at least one additional transmission opportunity is within the delay tolerance of the device; and in the case of no, controlling the transmitter to transmit a signal on the at least one available channel; and in the case of yes, waiting for one of the at least one additional transmission opportunities that is within the delay tolerance before controlling the transmitter to transmit at least one signal on the at least one available channel.

[0053] Further particular and preferred aspects are set out in the accompanying independent and dependent claims. Features of the dependent claims may be combined with features of the independent claims as appropriate, and may be combined differently than those explicitly set out in the claims.

[0054] Where an apparatus feature is described as being operable to provide a function, it will be understood that this includes apparatus features that provide that function or that are adapted or configured to provide that function. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] Some example embodiments will now be described with reference to the accompanying drawings, in which:

[0056] Figure 1 illustrates an example of transmission of replica signals on two sub-channels with and without interference, without self-delay, and a Type A1 LBT process without self-delay;

[0057] Figure 2 illustrates an example of transmission of a replica signal on two sub-channels with and without interference using self-deferral, a Type A1 LBT process with self-deferral;

[0058] Figure 3 illustrates an example of transmitting a replica signal on two sub-channels with and without interference, a Type A2 LBT process;

[0059] Figure 4 A flowchart illustrating steps in a method according to an example embodiment is shown;

[0060] Figure 5 illustrates an example of transmitting a replica signal on two sub-channels in the presence and absence of interference on one of the sub-channels using a method according to an embodiment; and

[0061] Figure 6 An apparatus according to an embodiment is schematically illustrated. DETAILED DESCRIPTION

[0062] Before discussing example embodiments in greater detail, an overview will first be provided.

[0063] Increasingly, devices are capable of transmitting and receiving on more than one channel, and this capability can be used to improve spectral efficiency and / or increase transmission reliability, for example, by transmitting duplicate data on more than one channel. However, if the signal is transmitted in unlicensed spectrum, since this bandwidth is shared with other devices, some channel scanning may be required before any transmission to determine whether a channel is available. Therefore, while transmitting on more than one channel can be advantageous where the channels used are relatively close in the spectrum, a device transmitting on one channel will be prevented from scanning another channel while transmitting on another. For the reasons mentioned above, when transmitting on more than one channel in unlicensed spectrum, it may be advantageous to transmit on multiple channels simultaneously. However, to do this, it must first be determined that both channels are currently available, and this requirement to wait for multiple channels to become available can result in increased latency. Specifically, if one channel is detected to be unavailable but another is available, a decision must be made as to whether to wait for both channels or transmit on the available channel. Choosing the latter means that the other channel cannot be scanned until the transmission is complete.

[0064] One example where transmitting over multiple channels is particularly effective is data replication. Data replication across multiple subchannels is used to increase transmission reliability. In unlicensed spectrum, data replication can provide additional robustness against LBT failures. When combining data replication with NR-U wideband operation, the transmitter needs to perform LBT separately on each configured / scheduled subchannel.

[0065] DL / UL channel access for multi-channel transmission supports different schemes, denoted as Type A and Type B.

[0066] In Type A, the transmitter performs Cat4 LBT independently on multiple subchannels. After successfully performing LBT on the first subchannel, the transmitter can either transmit only on the first subchannel or defer transmission until LBT succeeds on the second, third, and so on subchannels. In the latter case, the transmitter performs a shot-LBT on the first subchannel again before transmitting.

[0067] Type A1: LBT counter is determined independently for each carrier

[0068] • Type A2: The LBT counter is determined for the carrier with the largest value of the largest congestion window. The LBT counters for all other carriers are then set equal to this value (so that the LBT counters are initialized to exactly the same value on all carriers).

[0069] In Type B: The transmitter performs Cat4 LBT on a primary subchannel (selected by the transmitter at most once per second), or uniformly randomly selected from a set of carriers before each transmission on multiple carriers. After successful LBT on the primary subchannel, the transmitter performs LBT on the second, third, etc. subchannels.

[0070] Using the NR-U UL CG (New Radio Unlicensed Uplink Configuration Grant) framework, a UE can be allocated a semi-persistent UL transmission opportunity that can occur as frequently as every two OFDM (Orthogonal Frequency Division Multiplexing) symbols. Assuming an SCS (subcarrier spacing) of 60kHz, this may correspond to a transmission opportunity every ~35μs.

[0071] In the case of adjacent subchannels or subchannels with limited frequency separation, due to practical transceiver implementation issues, while transmitting on one subchannel, the transmitter can neither perform LBT nor initiate transmissions on other subchannels. Therefore, the start of transmission on the subchannel that first undergoes successful LBT will prevent transmissions on other subchannels during the channel occupancy time.

[0072] When a transmitter (e.g., a UE) wants to transmit URLLC (Ultra-Reliable Low Latency Communication) data simultaneously on multiple sub-bands (using, e.g., repetition / replication in the frequency domain), there is a dilemma: should the transmitter:

[0073] - Initiate transmissions on any subchannel as long as at least one subchannel is available for transmission. This may result in inefficiencies (e.g. only one subchannel is used at a time) that may negatively impact latency performance in the long run, or

[0074] Deferring transmission until all subchannels are available for transmission. If at least one of the subchannels experiences LBT congestion, this will obviously impact latency performance. It is also possible that all subchannels become busy while self-deferring, leading to even worse latency issues.

[0075] Consider an example scenario where a UE is assigned UL configured grant transmissions on multiple subchannels simultaneously (with repetition / duplication configured in the frequency domain):

[0076] For Type B multicarrier channel access, the transmitter selects a primary subchannel and performs Cat4 LBT on that subchannel. Only after Cat4 LBT on the primary subchannel succeeds can the transmitter perform Cat2 LBT on other subchannels. The primary subchannel can be selected at most once per second or once before each transmission based on a random selection. This option is not suitable for data transmission with low latency requirements, because LBT congestion on the primary subchannel will block transmission on all subchannels.

[0077] A UE using Type A LBT may be able to initiate a transmission on one subchannel (#1) while LBT on another subchannel (#2) is still in progress. If a transmission is initiated in subchannel #1, then the UE needs to stop LBT on subchannel #2. In this way, the UE reduces latency, but can effectively only transmit on one subchannel at a time. In the case of data duplication, in addition to reducing the reliability of the transmission (by transmitting on only one subchannel), this option may require complex mechanisms to perform duplication cancellation on the subchannels where there is no transmission, otherwise latency may be effectively increased due to the following reasons: (1) transmission only occurs on one subchannel at a time and (2) unnecessary domain multiplexing of data copies.

[0078] In this regard, Category 2 LBT is LBT without random backoff. This is a fast LBT that typically has a 25 microsecond listening period at, for example, 5 GHz and can be used for multi-channel access. Category 4 LBT is LBT with random backoff and a variable-sized contention window. The contention window length depends on the channel access priority.

[0079] Figure 1 An example of a type A1 (no self-deferral) multi-carrier access procedure for URLLC data transmission using replication is shown in the case of interference encountered on one of the carriers (A) and in the absence of any interference (B). We assume that the transmitter (UE) is allocated UL CG transmission on both channels / carriers. In the example, the UL CG resources are allocated with a periodicity of ~35μs (corresponding to ca. 4CCA time slots of 9μs). This example shows that no matter whether subchannel #2 is idle or busy, the transmitter (UE) always ends up transmitting only on subchannel #1 (the disadvantage is highlighted above) because the other subchannels are not available at the same time due to different LBT counters and there is no self-deferral to allow the UE to wait for subsequent channels to become available.

[0080] With Type A1 LBT, the transmitter can also perform self-deferral and wait until cat4 LBT succeeds on other channels. However, this option presents similar disadvantages as the above-mentioned Type B channel access in the event that one of the subchannels is blocked by interference. Figure 2 As shown in Figure A.

[0081] Figure 2 Figure 3: Examples of a Type A1 (with self-deferral) multicarrier access procedure using replicated URLLC (Ultra-Reliable Low Latency Communication) data transmission in situations where one of the carriers experiences interference (A) and in the absence of any interference (B). In this example, both devices transmit on both channels simultaneously at all times. This imposed delay is indicated by the length of the self-deferral time, and a significant delay may be introduced by one of the channels being busy. Therefore, in example A, subchannel #2 is busy. The LBT counter is then not decremented for the 4 CCA slots during and after the busy period, and therefore, there is a significant delay for both channels to be available. In the case where both channels are available during the scan shown in B, a delay would occur on channel #1 due to the difference in the LBT counter values. As can be seen, cat2 LBT is performed after the self-deferral to confirm that channel #1 is still available.

[0082] like Figure 3 Another option (Type A2) illustrated in FIG is to set the LBT counters on different subchannels to the same value based on the subchannel with the highest value of the maximum contention window. One advantage of this option is that, in the absence of interference on both subchannels, the independent LBT processes on multiple subchannels are synchronized and should succeed simultaneously (thereby avoiding transmission on a single subchannel when there is no interference on other subchannels). However, in the presence of interference on one of the subchannels, since the LBT counter is determined based on the subchannel with the highest value of the maximum contention window, transmission on the subchannel without interference may be unnecessarily delayed.

[0083] exist Figure 3 In Figure A, interference is encountered on one of the carriers (A), and in this example, without self-deferral, the transmission occurs on subchannel #1 instead of subchannel #2. While the transmission is occurring on subchannel #1, scanning cannot occur on subchannel #2, so the transmission is further deferred. In Figure B, no interference occurs, and when the LBT process is complete, the device transmits on both subchannels. The LBT process takes the same amount of time on both subchannels because the LBT counters are set to the same value.

[0084] To address many of these issues, embodiments provide a system in which a node, upon sensing that a channel is available, makes an informed decision about whether to transmit on that channel as soon as possible, or to delay and wait for additional channels to become available so that it can transmit on more than one channel together. This decision is informed by evaluating when one of the additional channels is expected to become available, and whether it is within a set deferral time. If this is the case, the node will wait and possibly re-evaluate later. If at any time the node determines that no other channels will become available within the set deferral time, it will choose to transmit on the available channel at the next available transmission opportunity. In this way, channel congestion is avoided because if any congestion is detected or estimated to be possible, the self-deferral will be canceled.

[0085] The embodiments propose a novel multi-carrier LBT (Listen Before Talk) mechanism for URLLC (Ultra-Reliable Low Latency Communication) data transmission over unlicensed spectrum with sub-1 ms delay requirement.

[0086] In an embodiment, the UE is assigned a set of UL CGs (uplink configuration grants), which are uplink transmission opportunities that share the same time domain configuration. The UE is also provided with a packet delay budget (or postponement tolerance) for a set of specific UL CG transmissions. The packet delay budget can be configured for a logical channel (LCH) or LCH group mapped to a corresponding set of UL CG transmissions. The packet delay budget provides the maximum time the UE is allowed to postpone signal transmission. In some embodiments, the packet delay budget is configured as the maximum number of UL CG transmission opportunities for which the UE can postpone data transmission on a subchannel after a successful LBT.

[0087] The decision on whether to perform self-deferral may be made at each UL transmission opportunity depending on: (1) the packet delay budget, (2) the value of the LBT counter in the other carrier, and (3) the channel status (idle / busy) of the other carrier.

[0088] An LBT counter N is maintained independently on each carrier (subchannel #1 and subchannel #2); after the LBT counter N is equal to 0 in one of the carriers (subchannel #1) and the UE is able to initiate transmission on the corresponding carrier; the UE checks the channel status on the other carrier (subchannel #2) (for example, whether the carrier is sensed to be idle or busy in the last CCA slot) and the LBT counter N. Based on the channel status in the additional carrier (subchannel #2) and the status of the LBT process (including the value of the LBT counter N), the UE evaluates whether channel access on at least one of the additional carriers (subchannel #2) can be successfully completed within the packet delay budget.

[0089] If yes, the UE postpones the data transmission on the carrier (subchannel #1) where LBT succeeded to the next transmission opportunity.

[0090] If not, the UE starts transmitting on the carrier(s) (subchannel #1) where LBT was successful.

[0091] At the next transmission opportunity, the UE may again evaluate whether channel access on at least one of the additional carriers (subchannel #2) can be successfully completed within the packet delay budget.

[0092] If yes, the UE postpones the data transmission on the carrier (subchannel #1) where LBT succeeded to the next transmission opportunity.

[0093] If not, the UE starts transmitting on the carrier(s) (subchannel #1) where LBT was successful.

[0094] The operation according to an exemplary implementation of the proposed invention is Figure 4 is shown in the flow chart.

[0095] At step S10, the UE starts a Cat4 LBT procedure on multiple sub-channels and continues scanning multiple channels, including using self-deferral where appropriate (S20), until:

[0096] The LBT procedure succeeds on at least one subchannel (Ci), i.e., a valid UL transmission opportunity is found (D5-Yes) and when the UE is ready to transmit on at least one carrier (D15-Yes), then

[0097] First the UE determines whether there are any other subchannels that can be used for transmission, but the LBT procedure has not yet succeeded (D25).

[0098] If not (NO), the UE initiates transmission on the available subchannel(s) at step S30.

[0099] If yes, the UE checks at D35 whether the channel status on at least one of the additional sub-channels (Cj, j≠i) is idle.

[0100] In one possible implementation, a subchannel is determined to be idle if the subchannel was sensed as idle during the last CCA (Clear Channel Assessment) measurement.

[0101] In an alternative implementation, a subchannel may also be determined to be idle if it was sensed as busy during the last CCA measurement, for example if the UE can estimate (based on past measurement samples) that the channel will become idle within a certain number of CCA slots.

[0102] In yet another implementation, a subchannel may be determined to be busy even if it was sensed as idle during the last CCA measurement, for example, if the UE can estimate (based on past measurement samples) that the channel will become busy within a certain number of CCA slots.

[0103] If the channel is busy on all other subchannels (D35 No) or the next UL Tx opportunity is not within the packet budget delay (D45 No), the UE initiates transmission on the available subchannel(s) at step S30.

[0104] In one embodiment, the packet delay budget is defined as the maximum number K of UL CG transmission opportunities that a UE can defer data transmission on a subchannel with successful LBT. In this case, if, for example, the UE is first ready to transmit on any available subchannel at UL Transmission Opportunity #n and the next UL Transmission Opportunity #n+K+1, the next UL Tx opportunity is not within the packet budget delay.

[0105] Otherwise, the UE checks the value of the LBT counter and the status of LBT (e.g., whether the UE is in the additional deferral mode - D55) on the corresponding subchannel(s), and estimates the shortest time the UE can successfully complete the cat4 procedure depending on the UE's situation in the deferral period at steps S40 and S50.

[0106] If it is determined at D65 that the time is within the packet delay budget for the at least one additional subchannel, the UE defers transmission until the next UL transmission opportunity and continues scanning other channels by returning to step S20 .

[0107] Otherwise, the UE initiates transmission on the available subchannel(s) at step S30.

[0108] Figure 5 The figure shows the transmission timing in the case of interference and in the case of no interference according to one embodiment. In this example, when subchannel #1 is available and has a transmission opportunity, subchannel #2 is busy. The UE determines that the LBT counter of subchannel #2 is set to 10 and the channel is currently busy. In this case, it determines that subchannel #2 is unlikely to become available and have a transmission opportunity within the packet delay budget for the UE, so it transmits a signal on subchannel #1 at the first available transmission opportunity.

[0109] In the second example, there is no interference, when subchannel #1 becomes available, the UE determines that the LBT counter in subchannel #2 is 8 and that the channel is idle, it determines that there may be a transmission opportunity on this channel within the packet delay budget, so it postpones transmission on subchannel #1 until subchannel #2 is available, and the two channels are used to transmit signals together.

[0110] Compared with the existing technical solutions, the advantages of the proposed channel access method are as follows Figure 5 The proposed method combines the advantages of type A2 channel access (synchronous channel access with no or limited interference on one channel) with the advantages of type A1 (fast channel access with interference on one channel in the signal) without self-deferral.

[0111] Figure 6 The diagram illustrates an apparatus or node according to an embodiment. Apparatus 10 is configured to transmit and receive signals on multiple channels within an unlicensed spectrum, schematically shown as bidirectional arrows 22, and may be, for example, a user equipment (UE) or a gNB. Apparatus 10 includes transmission circuitry 30 and reception circuitry 32 configured to transmit and receive signals on multiple channels of the unlicensed spectrum via antenna 20. Apparatus 10 includes scanning circuitry 40 configured to scan multiple channels in the unlicensed spectrum using a listen-before-talk process to determine whether they are available. In other embodiments, other scanning circuits using other scanning processes, such as clear channel assessment, may be used.

[0112] The apparatus 10 includes a control circuit 50 configured to control the transmission, reception and scanning circuits 30, 32, 40 to perform operations such as Figure 4 , whereby the device transmits a signal, possibly a replica, to at least one other node on one or more channels within an unlicensed spectrum. The device scans a plurality of channels within the unlicensed spectrum to determine at least one available channel. Upon detecting an available channel and before transmitting a signal on that channel, the device determines whether another channel from the plurality of scanned channels is likely to become available within a predetermined packet delay budget. If not, the device transmits the signal at a first transmission opportunity. If so, the device waits for the next transmission opportunity while continuing to scan other channels, and then performs the same evaluation again.

[0113] The packet delay budget can be set for a specific device, communication type or channel. It can be set centrally by the network or specific to the user device. It can be set to a time value or to a counter value that indicates the number of transmission opportunities. The network node can be configured to transmit a packet delay budget or a postponement tolerance to the user device. The network node can also transmit an indication of whether data replication is to be used and / or the listen-before-talk type to be used. The user device may include a component configured to receive a postponement tolerance signal and respond accordingly to set the postponement tolerance. It can be set for a given set of uplink configuration authorizations and can be configured by the network node. The determination of whether to postpone transmission and whether additional channels may become available in the packet delay budget can also be configurable and can depend on the current value of the LBT counter, the current availability, the historical availability and the current channel load and / or occupancy.

[0114] Those skilled in the art will readily recognize that the steps of the various methods described above can be performed by a programmed computer. Some embodiments herein are also intended to encompass program storage devices, such as digital data storage media, which are machine or computer readable and encode a program of instructions that are machine or computer readable or that are computer executable, wherein the instructions perform some or all of the steps of the methods described above. The program storage device can be, for example, a digital memory, a magnetic storage medium such as a disk or tape, a hard drive, or an optically readable digital data storage medium. Embodiments are also intended to encompass computers programmed to perform the steps of the methods described above.

[0115] Although embodiments of the present invention have been described in the preceding paragraphs with reference to various examples, it should be appreciated that modifications to the examples given can be made without departing from the scope of the invention as claimed.

[0116] Features described in the preceding description may be used in combinations other than the combinations explicitly described.

[0117] Although functions have been described with reference to certain features, the functions may be performable by other features whether described or not.

[0118] Although features have been described with reference to certain embodiments, those features may also be present in other embodiments whether described or not.

[0119] While efforts have been made in the foregoing description to draw attention to those features of the present invention which are regarded as particularly important, it will be understood that the applicants claim protection for any patentable feature or combination of features mentioned above and / or shown in the accompanying drawings, whether or not specifically emphasized therein.

Claims

1. An apparatus for communication, the apparatus comprising components configured to: initiating a scan of a plurality of channels in an unlicensed spectrum to determine whether the plurality of channels are available; determining a transmission opportunity in which the apparatus is able to transmit a signal on at least one channel sensed as available during the scanning period; When it is estimated that the apparatus may be able to transmit signals on at least one additional channel in the unlicensed spectrum, estimating at least one additional transmission opportunity; as well as determining whether a delay between the transmission opportunity and the at least one further transmission opportunity is within a current deferral tolerance for the apparatus, the deferral tolerance comprising a maximum period for which the apparatus can defer the transmission; and if not controlling the transmission of a signal on said at least one available channel; and in the event that Waiting for one of the at least one additional transmission opportunities that is within the current holdover tolerance prior to controlling transmission of at least one signal on the at least one available channel.

2. The apparatus of claim 1 , wherein the component is configured to estimate the time of the at least one additional transmission opportunity for the at least one channel based on at least one of: a determined state of the channel, and a backoff time associated with the channel; the backoff time being a minimum time delay before a transmission opportunity can occur if the channel is currently idle and remains idle.

3. The apparatus of claim 2, wherein the determined state of the channel comprises one of: a sensed state sensed during a previous measurement time period, or an estimated state based on the sensed state and a historical availability of the channel. 4 . The apparatus of claim 3 , wherein the previous measurement time period comprises a measurement period immediately preceding a most recent transmission opportunity.

5. The apparatus according to claim 1 , wherein the component is configured to determine whether any of the at least one additional channel of the plurality of channels is available at one of the at least one additional transmission opportunities, and if available, the component is configured to control the at least one signal to be transmitted on the at least one available channel and the at least one additional signal to be transmitted on the at least one additional available channel at the one additional transmission opportunity of the at least one additional transmission opportunity.

6. The apparatus of claim 1 , wherein the component is configured to determine whether all of the at least one additional channel of the plurality of channels are busy, and if so, control transmission of the at least one signal on the at least one available channel at a next transmission opportunity.

7. The apparatus of claim 1, wherein the at least one signal and the at least one further signal are the same signal, the apparatus being configured to transmit replica signals over a plurality of channels. The apparatus of claim 1 , comprising user equipment.

9. The apparatus of claim 1, wherein the component is configured to receive a signal indicating the deferral margin from a network node.

10. The apparatus of claim 1 , comprising a gNB. The apparatus of claim 1 , the one or more signals comprising a downlink signal.

12. The apparatus of claim 1 , wherein the component comprises: at least one processor; as well as At least one memory including computer program code, the at least one memory and computer program code being configured to, with the at least one processor, cause execution of the apparatus.

13. An apparatus according to any preceding claim, further comprising means for transmitting and receiving signals, and means for scanning channels in an unlicensed spectrum.

14. A method for communication, comprising: scanning a plurality of channels in an unlicensed spectrum to determine whether the plurality of channels are available; In response to determining that at least one of the plurality of channels is available, determining a transmission opportunity in which the device is able to transmit at least one signal on the at least one available channel; estimating at least one delay between the transmission opportunity and at least one further transmission opportunity at which it is estimated that the apparatus may be able to transmit a signal on at least one further channel of the plurality of channels; and determining whether any of the at least one delay is within a current deferral tolerance, the deferral tolerance comprising a maximum period for which the apparatus can defer the transmission, and if not transmitting the at least one signal on the at least one available channel; and In the case of Transmission of the at least one signal on the at least one available channel is delayed until another transmission opportunity is within the current holdover tolerance.

15. The method according to claim 14, Wherein said step of estimating said at least one delay comprises: estimating a time for the at least one additional transmission opportunity for the at least one channel based on at least one of: a determined state of the channel, and a backoff time associated with the channel; The backoff time is the minimum time delay before a transmission opportunity can occur if the channel is currently idle, and remains idle.

16. The method of claim 15, wherein the determined state of the channel comprises one of: a sensed state sensed during a previous measurement time period, or an estimated state based on the sensed state and a historical availability of the channel.

17. The method according to claim 14, further comprising: determining whether any of the at least one further channel of the plurality of channels is available at one of the at least one further transmission opportunities, and if so, At the further transmission opportunity, the transmission means is controlled to transmit the at least one signal on the at least one available channel and to transmit the at least one further signal on the at least one further available channel.

18. The method according to claim 14, further comprising: It is determined whether all of the at least one further channel of the plurality of channels are busy, and if so, controlling the transmission component to transmit the at least one signal on the at least one available channel at a next transmission opportunity.

19. A method according to any one of claims 14 to 18, wherein the at least one signal and the at least one further signal are the same signal, the method transmitting duplicate signals on a plurality of channels if such channels are available.

20. A computer-readable medium comprising computer-readable instructions which, when executed by a processor on a device, are operable to control the device to perform the method according to any one of claims 14 to 19.

21. An apparatus for communication, comprising: scanning circuitry configured to scan a plurality of channels in an unlicensed spectrum to determine whether the channels are available; a transmitter for transmitting one or more signals on one or more channels of the plurality of channels; as well as A control circuit, configured to control the transmission of the one or more signals, wherein the control circuit is configured to: enabling the scanning circuit to scan a plurality of the plurality of channels to determine whether the plurality of the channels are available; determining a transmission opportunity in which the device is able to transmit a signal on at least one channel sensed as available by the scanning circuitry; estimating at least one further transmission opportunity when it is estimated that the apparatus may be able to transmit signals on at least one further channel of the plurality of channels; as well as determining whether a delay between the transmission opportunity and the at least one additional transmission opportunity is within a deferral tolerance of the apparatus, the deferral tolerance comprising a maximum period by which the apparatus can defer the transmission; and If no, controlling the transmitter to transmit a signal on the at least one available channel; and If so, waiting for one of the at least one additional transmission opportunity that is within the holdover tolerance is performed before controlling the transmitter to transmit at least one signal on the at least one available channel.

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